QImage usage with un-dithered image causes memory leak.

QImage usage with un-dithered image causes memory leak.
On the otherhand the same code with a dithered image does not cause leak.

Please explain the difference.

QPalette clPalette;
QImage clImage("/home/test.png");
clImage = clImage.copy(0,26,320,215);
clPalette.setBrush(backgroundRole(), QBrush(clImage));
setPalette(clPalette);